The additional recovery of cooking coal middlings can be utilized for increasing of yield of concentrate cooking coal. Combination flow sheet of comminution and flotation can realize this target. To investigate the effect of grinding process on the further flotation of ground products, the progressive release flotation tests were used to compare with the float-sink tests, which were regarded as the criterion. Coal middlings were ground by wet-milling with iron balls to <0.5 mm. Curves of ash vs. cumulative yields of sized products indicated that yields of coal separated by progressive release flotation were lower than that of coal benefited by float-sink test, with the same ash for the four size fractions (0.5-0.25 mm, 0.25-0.125 mm, 0.125-0.074 mm and <0.074 mm). Distributions of elements conducted by Energy Disperse Spectroscopy (EDX) showed that the associated kaolinite was liberated and exposed on the surface. This led to the shift of local surface property from hydrophobicity to hydrophilicity. Meanwhile, analyses of chemical property performed by X-Ray Photoelectron Spectrometer (XPS) depicted that the hydrophilic mineral FeOOH, which generated in the grinding process, was adsorbed on the surface. Floatability of ground products were worsened due to the increase of hydrophilicity on the coal surface.